X-ray apparatus



Sept. 1, 1936. A. BouwERs X-RAY APPARATUS Filed June 14,l 1934 @Myra 254546 a@ 5 Patent ed Sept. 1, 1936 X-RAY APPARATUS Albert Bouwers, Eindhoven,

signor to N. V. Philips Netherlands, as Gloeilampenfabrieken,

Eindhoven, Netherlands Application June 14, 19

3 Claims. (C

VThis invention relates to certain improvements and mod type described in In 5 present application In my tain elec shellof space vides for fers furt tube i'orrns the load dev A selfoordance cation results in a more co smaller dimensions an known prior X-r formance.

ifications of electrical apparatus of the y copending application Ser. cember 21, 1 933, of which the forms a continuation in part. prior application I have described certrical apparatus in which a radial or 61, led De type transformer and a high tension load device closely surrounde 10 combined in a com of the apparatus r 'I'he present invention relates to various novel features making possible still further important reductions in weight andY overall dimensions of such a unit. For exam able for work, examination of c be made altogether dispensed holding the apparatus in the X-ra ple, a unit which is suitgraphic work, as dental ollar bone, hands, etc., can light, that a support can be with; the operator merely the hands when taking simple radio so small and y picture.

The improvements of the present invention comprise netic cor I have transformer yoke or core, which minimizes or altogether a more efficient cons e of the transfor truction oi' the magmer, and of the high tension insulation.

found that by a construction of the avoids the .interspaces between the individual lamination's of the core normally present in the ra 0- siderable paratus may be obtained.

instance,

5 instance,

dial shell-t reduction ype transformer, a very conin size and weight of the ap- This I achieve, for interspaces between tizable material, for with strips or pulverized material. Or

by filling out the again, the laminations, instead of having uniform thickness are increasing in thickness toward the periphery of the transformer.

This leads to a more eiiicient utilization of the space and a deo crease oi' 5 Accord the dimensions and the weight. ing to a further feature of my invention,

the aperture or window of the laminationsmay be forme which fa 55 former.

d as an isosceles trapezoid, the base of 11s towards the periphery of the trans- This, combined with a preferred ar- 34, serial No. 730,661

rangement of the transform more fully explained in connection with the drawing, permits a simpler coil construction, and a more eiicient arrangement of the high-tension insulation between the core and the transformer 5 coils, and results in further saving in weight and reduction in dimensions of the apparatus.

A still further feature is to have the envelope ofthe X-ray tube oppose the core with conductive members throughout the entire length of 10 the core and to bring these conductive members and the core at the same, and preferably ground potential.

Another feature of the inve support the X-ray tube in the transformer, the 15 support also acting as electrical connectors between the core and the metal portion of the envelope.

Further features of the invention will appear as the specification progresses.

In order that the invention may be clearly understood and readily carried into effect, it will be more fully described with reference to some embodiments thereof, and in connection with the accompanying drawing, in which:

Figure 1 is a sectionized front view of an X-ray apparatus showing one embodiment of my invention.

Figure 2 is an end view of the apparatus shown Figure 1, with certain parts removed. Figure 3 is two cross-sectional views arranged above and below a dot and dash line of transformer portions, one of which shows an embodiment of the present invention, and the other of which shows an embodiment according to the 35 prior application.

Figure 4 is a perspective view showing the lamination made in accordance with the present invention .and corresponding to the lamination in the upper portion of Figure 3. 40

Figure 5 is a cross-sectional view of a transformer portion showing a further embodiment of the invention.

The apparatus shown in Fi an X-ray tube having an ano a cathode structure 2. The X erably a cylindrical shape and comprises a metallic waist po ends of which are sealed resulating members 4 structure I and the c tively. While other t in connection with m an equipotential mid is highly desirable.

er windings, as will be ntion is to resiliently gure 1 comprises de structure I and -ray tube has prefis of the type which rtion 3, to the two entrant vitreous inand' 5 carrying the anode 50 athode structure 2 respecypes of tubes may be used y invention, the presence of dle section at the envelope The X-ray tube is closely surrounded by a cylindrical transformer which is coaxial with the tube. I

While the tube is shown to slightly extend be` yond the transformer on the two sides thereof, it may be ush therewith or even shorter than the transformer. Preferably the transformer and tube are so dimensioned with respect to each other that they are of substantially equal length, this giving as a rule, the most compact arrangement of the apparatus.

The transformer is of the so-called radial type" and comprises a laminated yoke or core, the lamination being of silicon steel or other similar material of high magnetic emciency.

The individual laminations 6, as shown in Figure l, have the general shape of a buckle or window frame comprising a central aperture 45. The laminations thereby comprise an inner and an outer axially extending-leg 45 and 41 respectively and two radially-extending connecting legs 413-48. The laminations are split as shown at 61 and can thus be bent open and slipped over the transformer coils when the transformer is assembled.

The apertures 45 of the assembled laminations form a cylindrical space in which are disposed the transformer windings together with their insulation. The transformer windings are subdivided into two coil assemblies, one assembly 49 being formed of a primary coil I and a secondary coil 9, and the other assembly 49' being formed of a primary coil 8 and a secondary coil I9. The primary coils 1 and 8 are the inner coils, and the secondary coils 9 and I0 are wound around them. The two primary coils l and 8, are connected A in series and the two secondary coils 9 and I0 are also connected in series. The preferred organization and the interconnections of the coils,

as well as their outside connections, will be` later described.

, Between the core and the coils is provided an insulating structure II, /which forms a cylinder of uniform thickness between the outside surface of the secondary windings and the core, and extends radially at the two ends of the windings, with decreasing thickness towards the tube. This decrease in insulating capacity, as will be shown later on, is made possible by the corresponding decrease of the voltage difference between the windings and the core. The trapezoidal shape of the aperture 45 of the laminations takes care of the inwardly decreasing thickness of the insula.

tion.

Furthermore, the height of the inner leg 46 of the lamination is greater than that of the outer leg 41 and the radial connecting legs 48--43 decrease in width from the inside to the outside. The reason for and the advantages of so shaping the laminations will be explained later on.

The transformer is closely surrounded by a cylindrical metal housing 22 provided at its two ends with rounded hoods 23 and 24.

Provided on the hoods 23 and 24, along the longitudinal axis of the tube are pivots 53 and 54, at least one of which (shown in the drawing as the right side pivot 54) is apertured. Through this aperture 55 pass the leads I2 and I3 for the outside connection of the primary winding and a ground wire 29.

The leads I2, I3 and 29 pass through the housing 69 of a time switch secured to the pivot 54, and form an electrical cord 10 carrying a plug (not shown) adapted to be inserted in a standard light socket. The time switch is electrically included in one of the leads I2 and I3, and the other leads are red through the housing e9 without interrup;

tion as schematically shown in dotted lines. Thel time switch is of the usual type having a time adjusting device 1I and a current closing device 'I2 o one dial.

As shown in Fig. 2, a radial recess I4 is provided in the core for the leads I2v and I3, which are connected to the opposite ends ofthe primary windings 8 and 1 respectively, the other ends of which are connected at 65. The ground wire 29 is connected to the core (as shown at 38), to which is also connected the junction point or midpoint of the secondary windings 9 and I0. Preferably an insulator I5 is also provided for the mechanical and electrical protection of the leads I2, I3 and 29.

The anode structure I comprises a cylindrical body 56 of copper or other good heat-conducting metal which carries a target 39 of tungsten or other refractory metal.

The anode body 56 may be fused directly to the reentrant portion of the vitreous cylinder 4, preferably bymeans of an intermediate chrome iron member.

Instead of using a single piece anode body I prefer. for convenience of assembly to make it of two pieces, whereby a copper body 51, which is rounded at its outer end, is ttingly inserted into a corresponding cavity of the body 56 and serves to provide a. suiciently high heat capacity.

For the leads which connect the secondary winding with the electrodes a recess 60 is provided in the core (see Fig. 2). The free end 58 of the high voltage coil 9 is connected by lmeans of a coiled wire I1 to the anode body 51,

the lead I1 being surrounded by an insulating tube I6 of high insulating capacity, for instance of glass. The wire I1 is made in the form of a spring so that a good contact is obtained between this wire and the body 51 to which it is applied without being secured thereto.

The free end 59 of the secondary coil III is connected by means of a lead I9 toone end of the cathode-illament 20, and a tap 63 provided on the secondary winding close to terminal 59 is connected by means of a lead I8 to the other end of the filament; the voltage between the taps 59 and 63 being of such value as to bring the lament 20 to the desired operating temperature. The leads I8 and I9 are surrounded by an insulating tube 2l of high insulating capacity, for instance of glass. 1

The insulator I I forms suitably shaped pockets 6I-6I around the outer endsof the insulating sleeves I6 and 2|. l

'I'he housing 22 is electrically connected-to the core and is thus grounded, when during the operation of the apparatus the lead 29 is connected to ground. In. order to prevent rattling, a resilient layer 68 for instance voi felt is provided between the transformer andthe housing 22. As stated before,the transformer closely surrounds the X-ray tube, but instead of snugly inserting the tube in the transformer, I prefer to provide a resilient support for the tube. For this purpose I provide contact springs 43-43, which embrace the metallic portion 3 of the tube and directly contact with the core. The'- springs 43-43 thereby also establish electrical connection between the core and the metal portion 3 and thus ground the latter, when thelead 29 is connected to ground.

The metal portion 3, while forming a comparatively large portion of the outer envelope of the short tube, and extending on both ends beyond the voperative portions of the electrodes, does not extend the full length of the core.' However, metal foils 44-44, which I provide at the metal-glass seals 64-64 to protect in accordance with the teaching of my U. S. Patent 1,824,755 the glass against puncture at the seal, I extend to points 62-62 at the ends of the core. Thus the entire length of the metal core is opposed by either the metal portion 3 or by the metal foils 44-44. Thereby, during the operation of the tube those portions of the insulating cylinders 4'and 5 which fall between the points 62 and the sealed joint of the respective electrode take up each one-half of the operating y voltage.

To prevent flash-over between the high tension parts and the housing, I provide the housing at its rounded hoods with insulating coatings shown at 25 and 26. Similarly, to prevent flashovers between high tension parts and the transformer core, the latter is provided at its frontal ends and around the corners with insulation, for instance coatings 21 and 28.

The X-rays produced at the target 39 of the anode, emerge from the tube through a raywindow 30, shown as a-glass window sealed into the metal sleeve 3. Opposite to the ray-window the housing 22 is provided with an opening 33, surrounded by an outwardly extending bushing 31'., serving for the attachment ofa centering tube or cone (not shown).

To minimize the absorption of X-rays by the insulating cylinder II, this cylinder is considerably weakened at its portion intercepting the X-rays as indicated at 3|. The reduction of the insulating capacity at this point can be accomplished without danger as at this point the core is also interrupted.

The apparatus is preferably provided with a U-shaped arm 4| on which lit is pivotally suspended by means of the pivots 53 and 54. The arm 4I is preferably rotatably mounted on a shaft 64, the axis 42 of which passes through the focal spot of the tube and is perpendicular to the longitudinal axis of the tube.

The apparatus, due to its pivotal suspension on the arm 4l, is also rotatable about the longitudinal axis of the tube.

In View of the radial, rather than parallel arrangement of the laminations 6 of the core, laminations having a uniform thickness cause interspaces to form between adjacent laminations, and as is shown in Fig. 2 the width of these interspaces increases towards the periphery of the transformer.

While such interspaces are generally regarded as desirable because they promote air circulation and thereby increase the heat dissipation and thus the load capacity of the transformer, I have found that the partial or preferably complete filling out oi such interspaces with a material having magietic properties suitable for a magnet core, results in very marked advantages.

More specifically I have found that by such filling out of these interspaces, the diameter of the transformer can be considerably reduced and for a given load capacity, smaller dimensions and less weight are required, or for a given weight and volume, the load capacity'of the transformer is increased compared with a transformer having interspaces between the laminations.

Figure 2 shows the end view of the apparatus of Fig. 1 seen from the right, with vthe hood 24 and the insulators omitted.

As shown in Figure 2, the interspaces between legs 41 of the laminae .are lled out with strips 35 of magnetic material, whereby the outer portion of the yoke forms a closed cylinder.

For instance, as shown in the drawing, by inserting in the interspace between adjacent legs 41, two strips 35 having the same thickness as the laminations, the iron cross-section of ,the outer portion of the yoke is increased threefold and thus the height of the legs 41 can be reduced to about one-third.

Thus the diameter of the transformer and hence of the whole device can be correspondingly reduced.

For the strips 35 the waste material which results from the stamping of the window 45 of the lamination can be utilized.

-If desired the remaining interspaces between adjacent lamellae, thus betweeen the legs 48-48 and 46, can be filled out with suitable powered magnetic material thus forming a completely closed yoke body.

A somewhat more expensive but still more emcient construction is obtained by making the laminations, instead of a uniform thickness, of a thickness which increases toward the periphery in such a manner that the assembled laminations form a completely closed and solid hollow cylindrical body. The laminations 36 of such a yoke are shown in Fig. 4, and also in Fig. 3 above the dash and dot line. Below the dash and dot line of Fig. 3, a portion of a transformer is shown designed for the same load capacity and made according tothe prior construction, in which the laminations 31 are united to form bundles.

Not only can the outside diameter of the transformer and of the apparatus be thus decreased, but also its length. This is accomplished because the filling out of the interspaces between the portions 48-48 of the laminations increases the effective magnetic cross-section, taken in the cylindrical plane of the legs 48, and thus the width of the legs can be reduced without reducing the magnetic cross-section. It is evident that by reducing the width of the legs 48-48 the total axial length of the apparatus can be reduced.

The above stated reduction of the width of the legs 48-48 of course depends upon the amount of the magnetic material which is added to fill out the interspaces between the laminations, and as this amount increases toward the periphery the width of the leg 48 may be and is decreased towards the periphery. Thus the width of the leg 48 gradually decreases from a value A, (which substantially corresponds to the height of the leg 46', shown as B), to a dimension A1, (which substantially corresponds to the height of the leg 41, shown asB1). Thereby the aperture of the iamination has a cross-section of an isosceles trapezoid. For the purpose of saving weight the laminations are rounded at the corners 66 and 14. Rounding the corners 66 is also-advantageous in4 preventing flash-overs.

In connecting the secondary windings, as above discussed, namely with the mid-point of the windings grounded at 38, the potential increases towards the periphery of the transformer, and it; is evident that the required insulation between the frontal ends of the coils and the adjacent legs 48 of the yoke has to radially increase in thickness. In such case the insulation requirements are met by an insulation I I, the general shape of which has already been described, and the thickof the yoke and of the insulation li results in a:

transformer which has the shortest axial length.

Ihe inner ends of the primary and secondary coils are tapered, as shown at 13, so that the air- I gap between the coils increases toward the periphery of the transformer with the increasing voltage. This tapering gives the further advan- T tage that the coils donut-intercept the emerging X-ray beam. Y

In Figure 5 a further embodiment is shown in which the laminations have a uniform thickness and the interspace 40 between the laminations is filled out with a powdered magnetizable material, such as iron powder of suitable permeability. The results obtained are similar to those obtained with the embodiment shown in the upper part of Figure 3. While the arrangement of Fig.`5 is less expensive than that according to Figure 4, it is somewhat less eiiicient in view of the fact that the magnetic lines of force are interrupted in the portions composed of powdered material.

An X-ray apparatus manufactured according to the invention is extremely compact and small in size. The self-contained apparatus, including the transformer and the tube, adapted to be connected directly to the light plug and suitable for voltages up to from 30 to 40 kilovolts, can be built having a diameter of 4 inches and a length of seven inches and with a weight of only about fifteen pounds. Such an apparatus, which can be used in dentistry or in lother types of radiography, for example, examinations of the hand, collar bone, etc., can be used with a very light standard or altogether without a standard; the apparatus being held in the hands.

The same principle, of course, can be applied to apparatus of larger capacity. In every case,

however, a great saving in Weight and size is obtained by applying the principles of my invention.

Nor is my invention limited to electrical apparatus, lof which the load device'consists of an X- ray tube, but the same principle can be applied to other types of apparatus.

Also various departures from the embodimen shown can be made without departing from. the spirit of the invention.

What I claim is:

1. A radial shell-type transformer comprising a hollow yoke and windings disposed within the hollow of said yoke, said yoke comprising radiallydisposed laminations of magnetizable material, said laminations having an apertured rectangular cross section, the axial width of said aperture increasing towards the periphery, and an insulator between said windings and said, yoke, said insulator having radially extending portions the thickness of which decreases from the periphery and in a radial direction to the same extent as increases the axial width of the aperture.

2. A radial shell-type transformer comprising a cylindrically-shaped core provided with an annular cavity whose axial width increases towards the periphery, windings disposed within the cavity of said core, and a member of insulating material disposed between the windings and the core and having radially-extending portions whose thickness increases toward the periphery.

3. A radial shell-type transformer comprising a hollow m'agnetic core having a central cylindrical bore and a magnetic circular thickness which increases toward the periphery of the .transformer, primary and secondary windings disposed in the hollow of said-core, the end surfaces of said core and said windings being perpendicular to the axis of the transformer, said core having radiallyextending legs whose axial width decreases toward the periphery of the transformer to form between the end surfaces o f said windings and the adjoining surfaces of said core spaces whose width in the direction of the transformer axis increases toward the periphery, andan insulating member disposed between said core and said windings, said member having radially-extending portions whose width in the direction of the transformer axis decreases toward said axis, said portions fitting in the spaces -between the core and the end faces of said windings.

ALBERT BOUWERS. 

